The present invention relates to an oil pan of an engine mounted on a vehicle. More particularly, the present invention pertains to an oil pan that has a sub-oil chamber to increases the volume of an oil reservoir and to an apparatus for forming such oil pans.
A typical vehicle engine includes an oil pan fixed to the lower part of the cylinder block. The oil pan has a reservoir for storing oil, which is supplied to the moving parts of the engine. The reservoir must be large enough to store the oil required by the moving parts of the engine. However, the size and shape of the space allocated for the engine in the engine compartment limits the vertical dimension of the oil pan, which may restrict the volume of the oil pan. If the oil pan is formed by deep-drawing sheet metal, the vertical dimension of the oil pan is limited by the deep-drawing process. Therefore, even if an adequate space exits in the engine compartment, the oil pan cannot be made deep enough. As a result, the volume of the reservoir is not sufficient.
Insufficient reservoir volume causes the oil to deteriorate in a relatively short time. Therefore, the moving parts of the engine are not sufficiently lubricated. Insufficient lubrication wears the moving parts, which increases engine vibration and noise and lowers the fuel economy. The oil, therefore, must be frequently changed.
If the volume of the reservoir is too small yet the reservoir stores a sufficient amount of oil for the engine to function normally, the level of the oil becomes relatively high. The oil in the reservoir is vibrated by the engine, which causes the oil to interfere with moving members such as the connecting rods and the crankshaft. This increases rotational resistance, creates bubbles in the oil, increases the oil temperature and degrades the oil.
To solve this above problem, oil pans having baffles have been introduced. A baffle is fixed to the inner wall of the reservoir and extends over the surface of the oil such that oil contacts the baffle when vibrated. The baffle needs to be fixed to the inner wall by welding, which complicates the manufacture of the oil pan. Further, the joint between the baffle and the oil pan may deteriorate or fail due to engine vibration and to the force of the vibrating oil.
FIG. 15 shows a prior art oil pan 100. The oil pan 100 has sub tanks 101 to increase its volume. The sub tanks 101 are separately formed and welded to the side walls 102 of the oil pan 100. A side chamber 101a, which is defined in each sub tank 101, is connected to the reservoir 100a of the oil pan 100. However, since the sub tanks 101 are formed separately from the oil pan 100 and the sub tanks 101 are welded to the oil pan 100, the manufacturing process is troublesome. Further, the joints between the sub tanks 101 and the oil pan 100 are easily damaged and deteriorate quickly.